Radio system



Sept. 1, 1931. f F. A. KOLSTER V 9 9 RADIO SYSTEM Filed June 26, 1928UNITAEY C3 CONT2OL IN V EN TOR.

A TTORNEYS.

f eder/Z-k A ko/sfa/f Patented Sept. 1, 1931 UNrrn srrss rarer oFFicsFREDERICK A. KOLSTER, OF IPALO ALTO, CALIFORNIA ASSIGNOR TO FEDERALTELEGRAPH COMPANY, OF SAN ERANCIgCO, CALIFORNIA, A CORPORATION OFCALIFORNIA RADIO SYSTEM I Application filed June 26,

This invention relates to radio signaling systems and particularly tosystems for the directive reception of signals.

. 7. An object of the invention is to provide radio receiving meanshaving pronounced directional characteristics. 7

The above object is achieved by so placing two bilaterally directiveantennae that the directions of maximum efficiency of the'separateantenna are 90 apart and so associating them in an electric circuit thatthey produce, on a detecting device, a cumulative signaling effect inresponse to signals from one direction while producing little or noeffect in response to signals from other directions.

Referring to the drawings Figure 1 is a circuit diagram illustrating thepreferred form of connecting the apparatus which I utilize in my systemand method.

Fig. 2 is a view illustrating diagrammatically the characteristics of mycombined system and method.

The system of this invention may be outlined briefly as comprising apair of directive radio antennae arranged so as to be directed alongintersecting paths, and connected to conjointly effect a radio receiver.The reactance of the several elements and the inductance of the antennaeare proportioned so that the system provides the same resonant periodfor any one setting of the system irrespective of the direction fromwhich signals are received.

The drawing depicts a pair of directive antennae 11 and 12, in the formof loops having a relatively small distributed capacitance and highfrequency resistance, and comparatively high lumped inductances. Theloop antennae are arranged in planes at an angle to each other, thepreferred angle being about 90 degrees as shown. A suitable signalingcircuit 13 is connected so as to be jointly in fluenced by bothantennae.

The system and method of this invention is particularly useful for radioreceiving systems and therefore signaling circuit 13 is shown asconsisting of suitable means for receiving and detecting radio signals.In this connection it is preferred to employ radio 50 frequencyamplifying means utilizing elec- 1928. Serial No. 288,462.

tron relays 14 and 15 of the usual three ele ment type. The grids ofrelays Hand 15 are connected to corresponding terminals of loop antennae11 and 12, by means of conductors 24L and 25. The plates of relays l4and15 are connected together and are energized from a suitable source ofpotential represented by the B battery 16. For coupling the remainder ofthe receiver with the out put circuits of relays 1 1 and 15, there 6Qshown a coil 17 connected in series with B battery 16, and this coil isshown as coupled to the input circuit of a suitable detector 18. Theenergy in the output circuit of detector 18 is preferably amplified in asuitable audio frequency amplifier 19 before being impressed upon atranslator 21. Suitable grid leaks 22 are connected between the gridsand filaments of the relays, and a suitable C battery 28 is inserted inthe cathode-grid path common to the two tubes for maintaining a negativebias upon the grids. .The cathodes of relays 14 and 15 preferably have acommon energizingcircuit provided with a suitable ground connection 26.p f

It is commonly known that a single loop antenna is bilaterallydirective, that is, it is directive in two directions along a linearaxis; A curve representing the directional characteristics of such aloop is theoretically a fig ure 8. It has been found that by properlycombining two loop antennae, the directional characteristics ofthe'resultant system can be made more accentuated than thecharacteristics of a single loop" antenna. "To obtain 35 this result,there is employed, in addition to the apparatus described above a pairof variable condensers G and G which are con nected in series acrossconductors 2 1 and Likewiseconnected directly across conduc- 9otors 24kand 25and there-forein shunt with series condenser C and C there isanother condenser C In addition to thgse condensers, there is providedan inductance coil L having one of its terminals connectedto cOr- $5"responding terminals of loops 11 and 12, and its other terminalconnected to theconductor interconnecting series conden'sersCi and C Thelumped inductance of loop 11' is made I substantially the same as thelumped inductance of loop 12, and the inductance of coil L issubstantially the same as to that of each of loops 11 and 12. Likewisethe condensers C C and C have equal capacities. In order to tune thesystem for different wave lengths, the capacitance of each of thecondensers is varied, and for this purpose these condensers are madevariable and are preferably mechanically actuated by means of a singleunitary control, For any one setting of the unitary control, thecondensers each have the same capacity.

The system as explained above has a pronounced directionalcharacteristic, which is represented aproximately by curve 3 of Fig. 2.This curve is plotted along the polar axes 1 and 2, the axis 2corresponding to the direction of maximum response. 4 ssuming that theoutput circuits of relays 14 and 15 are connected in parallel as in Fig.1, then the axis 2 of Fig. 2 corresponds to the direction indicated bythe dot-dash line 4 of Fig.1 Line 4 is drawn to biseet the angle formedby the planes of loops 11 and12. If the output circuits of relays 14 and15 are differentially connected then the direction of maximum responseis substantially at right angles to line 4, and line 4 represents thedirection ofminimum response, Loops 11 and 12 have their terminals soconnected to the remainder of the apparatus, that when receiving signalsfrom a direction represented by line4, impulses impressed upon the gridsof relays 14 and 15 will be in phase or of the same sign at any oneinstant.

The manner in which the above system operates may be explained asfollows: As previously mentioned, a single loop antenna hastheoretically a figure 8 directional characteristic and the direction ofmaximum reception is parallel to the plane of the loop. The directionsof the planes of loops 11 and 12 have been indicated by lines 5, and thedirection at right anglesto line 4 is represented by line 6. Assumingfirst that signals are being received from directions parallel to line4, then it is evident that currents of equal intensity Will be inducedin loops 11 and 12-. Because of the manner in which terminals of theseloops are connected with the remainder of the apparatus, potential im=pulses of the same intensity and of the same phase relationshipareimpressed upon the grids of relays 14 and Therefore amplified currentvariations in step with the potential variations impressed upon thegrids are caused to flow in the output circuits of relays 14 and 15,which are cumulative with respect to the coil 17, and effect a res onsein the translator 21. Assuming a secon case in which signals are beingreceived along directions parallel to the plane of loop 11, then currentisinduced in loop 11 but no current is induced inloop 12 since the planeof this loop is at right angles to the direction from which signals arebeing received. The effect of excitation of loop 11 causes impulses tobe impressed upon the grids of relays 14 and 15 which are of oppositesign at any one instant, so that no corresponding current variations areproduced in coil 17. Assuming a third case in which signals are beingreceived along directions parallel to line 6, then curents are againinduced in both loops '11 and 12, but these currents are 180 degrees outof phase. Therefore at any one instant, the potentials impressed uponthe grids of relays 13 and 14 are of opposite sign, hence they producecurrents in the output circuits of these relays which are equal but ofopposite sign so that they neutralize each other, and therefore produceno corresponding current variations in coil 17 i It can be demonstratedtheoretically that for any one setting of the apparatus, the system isresonant to one frequency irrespective of the direction from whichenergy of that frequency is received. Assuming again the first case inwhich signals are received from directions parallel to line 4, twoseparate reactive paths are provided for current flowa Designating loops11 and 12 as inductance L and L respectively, then one path is providedby inductance L condenser C and inductance L and another path isprovided by inductance L condenser G3 and inductance L The two circuitsare interrelated in that inductance L is in common to both.- Incomputing the period of the circuit arrangement for this case,inductance L and L are to be considered as functioning in parallel andeach of these inductances are to be considered as in series withinductance Lg; Condensers C and C are likewise to be considered as inparallel. tials upon conductors 24 and 25 are equal at any one instant,condenser G has no effect upon the circuit. The expression representingthe product of inductance and capacitance for this case can therefore bewritten as follows:

In the above ex ression L represents the inductance value to whichinducta'nces L L and L are each equal, and C represents the capacitancevalue of any one'of condensers C C and G which are equal. The aboveexpression reduces to the following:

% 20 which reduces to 3L0 2 Therefore for the first case considered, theproduct of inductance and capacities is equal to3LG.

For the second case, that is for signals re ceived along directionsparallel to line 5, current flow is along a path formed by in- Since thepoten- 1 ducta-nce L condenser C and inductance L In shunt withcondenser C and inductance L are the series connected elements C and LFor this case no potential difference will occur across condenser C sothat this condenser has no effect upon the system. The product ofinductance and capacitance for this arrangement can be written:

(L 20 which reduces to 3L0 (3) The system is therefore rendered automatically resonant to signals received along directions parallel to line5, when resonant to the same signals received along directions parallelto line 4.

For the third case, in which signals are received parallel to line 6, apath for current flow is formed by inductance L condensers C and C inseries and inductance L and a shunt path is formed about seriesconnected condensers C and C by condenser 0 At any one instant nopotential difference occurs across the terminals of inductance L andtherefore this inductance has no effect upon the circuit. For thiscondition the product of inductance and capacitance can be written:

2L C) which reduces to 3L0 (4) Expression 4 reduces to the same value of3L0, thus proving that the system is resonant to the same frequencyirrespective of the direction from which the radio energy is received.As explained above however the distribution of energy to the relays 14and 15 is such that when receiving signals along directions indicated bylines 5 and 6, substantially no current variations are produced in coil17 while when receiving along the direction indicated by line 4, amaximum response is produced. Although in the above theoreticaldiscussion only three cases have been considered represented by thedirections of lines 4, 5 and 6, it is obvious that the system will beresonant to waves of the same frequency received from all otherdirections. Thus if loop antennae 11 and 12 are mounted upon a suitableframe rotatable about a vertical axis, then when receiving signals fromany one transmitter, the system will remain in resonance with thefrequency to which it is tuned as the antennae are rotated thru 360degrees.

The described system provides a radio system having pronounceddirectional characteristics. Such a system is useful for reducinginterference when communicating between two stations, or may be employedas a radio compass for taking direction bearings.

I claim:

A radio system comprising conjugate loop antennae having their planes inangular relation, a coil having an inductance equal to my hand.

FREDERICK A. KOLSTER.

